This concerns the ETA/Unitas 6497 movement. This is probably something that I could look up, buy as usual I want to get your wisdom on this.

I have three watches that use the above mentioned movement; not clones, but genuine 6497s. What is perplexing to me is that each one requires a different amount of turns to fully wind. One goes into the fifties, while the other two are in the forties range. Oh, and yes, they are totally dead before the winding. Doesn't bother me, but have long been curious about it.

A thought just hit me (an unusual occurrence that has left me a bit woozy at the moment). :>) Are all Unitas movements made in the same facility, or does ETA farm some of their work out? If so that may account for it.

Actually, Gary, you did. Yes, my turns are consistent, as I believe everyone's would be. I also think that you are on to something with the car analogy. I had not thought of that. I was thinking more along the lines of different places of assembly, not the assembly itself. Furthermore, DON PM'd and told me something that I had not know of before. The movement comes in two variations --- one and two. My watches don't state on them which variant is doing the moving. Also, I did not know about the crown size affecting the turns., but evidently it does.

Like I said, it was just something that I have long been curious about. You, and the fellas have helped straighten this out for me, and I thank you all.

the smaller the crown the fewer the number of "winding movements" between the forefinger and thumb it will require to fully wind the mainspring compared to a larger crown. In other words a smaller crown turns more times per wind than a larger crown.

Messages: 280Location: West Suburbs of Chicago
Registered: November 2003

Re: mayor10's dumb question of the month...

Thu, 08 March 2018 20:21

Could it be that one of the movements is in a "better state of tune" than the other two? By that I mean the watch that requires the greatest number of turns is able to continue running with the mainspring exerting less force on the train/escapement. Thus the watch is still able to run with the mainspring more unwound than the other two watches. Perhaps the lubrication is a little better or the escapement is more in beat.

It should be easy to test this by winding and setting all three watches and seeing if the watch that requires the most turns also runs the longest.

Re: A "turn" is also dependent on the diameter of the crown. If they are different.....

Thu, 08 March 2018 21:00

Jim, whether a newbie or a seasoned veteran of the watch game, you never stop learning. Fortunately, this is a good place, populated with darn sharp guys, to ensure that that learning is available. Hey, for going on nine years these fellas have put up with me. Of course, it might have hurt me a bit to actually see their faces and hear their private comments while they were doing it. :>) Take care, bud. Karl

I don't currently own any manual wind watches, and I'm not sure I'd count the turns if I did....

As for the differences in turns you're experiencing, my first thought was that your watches had different diameter crowns. That's already been covered by other replies. For pure speculation, I'd say 2 factors could be:

- The mainsprings are from different manufacturing batches, and have different elasticity, but are still within ETA's tolerances;
- The mainsprings have different elasticity due to wear;
- The mainsprings were installed with slightly different "preload" when the movements were manufactured.

No, none of the watches have been serviced. As far as I can tell each each one is not ready for that as yet. In all due candor, only only one of them I know was brand new. The other two are pickups from the Sales Corner, and their service history is unknown by me. BTW, these two are the ones with the lower wind count. Thanks, bud. Karl

I wonder if it's possible that each watch reaches its "wound all the way down" point with different amounts of mainspring remaining wound in the barrel. This plus the difference in "gear ratio" created by varying overall diameter of the different crowns would be the two factors I guess could be at play.

You just may be right, Jeremy. Roger suggested a test of just that. When the one winds completely down I'm going to make that test. Thanks for participating, pal. I have learned quite a bit from this. Karl